Currently, the remote transfer and display of video data using consumer electronics devices has become a field of significant development. Generally, it is desirable to permit such streaming between devices with different display capabilities. With the advent of higher resolution video, it is desirable to compress the video stream to increase the amount of data that can be transferred, yet it is also desirable to permit viewing of such video streams with devices that may only permit lower resolution video streams or may have throughput or slow processing capabilities that render such higher resolution signals impracticable. Thus, scalable video streams are increasing in popularity. In general, a video bit stream is called scalable when parts of the stream can be removed in a way that the resulting substream forms another valid bit stream for some target decoder, and the substream represents the source content with a reconstruction quality that is less than that of the complete original bit stream, but is high when considering the lower quantity of remaining data.
The usual modes of scalability are temporal, spatial, and quality scalability. Spatial scalability (also referred to as spatial resolution) describes cases in which subsets of the bit stream represent the source content with a reduced picture size. Temporal scalability (also referred to as temporal resolution) describes cases in which subsets of the bit stream represent the source content with a reduced frame rate. With quality scalability, the substream provides the same spatial-temporal resolution as the complete bit stream, but with a lower fidelity—where fidelity is often informally referred to as signal-to-noise ratio (SNR). Quality scalability is also commonly referred to as fidelity or SNR scalability.
In systems that support spatial, quality and temporal scalability in real time, memory bandwidth can become a limiting factor in the overall system performance. Thus, the need exists for a way to reduce or eliminate the effects of read/write activity that can increase memory bandwidth issues.